RAPID: A Community Test of Distributed Acoustic Sensing on the Ocean Observatories Initiative Regional Cabled Array

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In recent years, there has been interest in the potential of offshore distributed acoustic sensing (DAS) in the Pacific Northwest and a test in this region would be of widespread interest to the oceanographic community. DAS is a relatively new observational technique in academia that interrogates an optical fiber with repeated laser pulses and utilizes changes in the phase of backscattered light to measure the strain rate along the fiber. DAS can work to distances of up to ~100 km, has a spatial resolution of a few meters and a broad frequency sensitivity. There is still a lot to be learned about how the DAS signal responds to strain. On land, DAS has been demonstrated for a wide variety of applications including earthquake monitoring and rapid response aftershock studies etc. DAS experiments in the ocean are more challenging. It wasn’t until 2019 that the potential of seafloor DAS for academic research was demonstrated. The Oregon margin is one of the most energetic coastlines in the world and an excellent location to test the DAS capabilities and is thus, an ideal site to study the role of storms in generating seismic noise near coastlines and potentially understanding if and how DAS could be used for measuring sediment exchange. DAS has also been identified as a new technology that might form an important component of future offshore earthquake and tsunami early warning systems in Cascadia and elsewhere. The scheduled shutdown provides a great opportunity to test DAS in this region. A Caltech graduate student will get experience leading data acquisition and two UW graduate students will gain experience in DAS/DTS data acquisition. The PIs are taking advantage of a rare scheduled shutdown in early November 2021 of the Ocean Observatories Initiative (OOI) Regional Cabled Array (RCA). With the RCA cables disconnected from all RCA shoreside equipment, the distributed acoustic sensing (DAS) and distributed temperature sensing (DTS) systems will be connected to the OOI fibers and will undergo testing to determine the potential of submarine DAS to observe seismic, oceanographic, acoustic and geodetic processes. DAS is potentially of great importance for efforts to develop offshore earthquake and tsunami warning systems in Cascadia and this experiment represents an important step in developing protocols that can support the use of DAS for science and hazards mitigation in the Northeast Pacific while meeting national security requirements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.